Nonpolarized magnetic reed switch

ABSTRACT

A NONPOLARIZED, SINGLE POLE, DOUBLE THROW DRY REED SWITCH CONSISTING OF AN ELONGATED ENVELOPE WHICH CARRIES THREE REED MEMBERS, TERMINATING, RESPECTIVELY, IN FIRST, SECOND AND THIRD CONTACT ELEMENTS THAT ARE POSITIONED WHOLLY WITHIN THE ENVELOPE. THE FIRST CONTACT ELEMENT IS RESILIENT AND FLEXIBLE AND PROJECTS INWARDLY FROM ONE END OF THE ENVELOPE. THE SECOND AND THIRD CONTACT ELEMENTS ARE ESSENTIALLY RIGID, PROJECT INWARDLY FROM THE OTHER END OF THE ENVELOPE AND ARE SPACED APART. THE FREE END PORTION OF THE FIRST CONTACT ELEMENT IS POSITIONED IN THE SPACE BETWEEN THE SECOND AND THIRD CONTACT ELEMENTS AND NORMALLY AND YIELDINGLY MAKES CONTACT WITH THE SECOND CONTACT ELEMENT. ALL REED MEMBERS, INCLUDING THEIR CONTACT ELEMENTS, ARE HOMOGENEOUSLY FERROMAGNETIC. BY PROPER SELECTION OF PARAMETERS OR COMBINATIONS OF PARAMETERS, SUCH AS THE COMPOSITION AND EXTENT OF ANNEALING OF THE REED MEMBERS AND THE CONFIGURATION AND ARRANGEMENT OF THE CONTACT ELEMENTS, THE PRESENT REED SWITCH EMBODIES IMPROVED OPERATING CHARACTERISTICS, SUCH AS EFFECTIVE SNAP ACTION, AS COMPARED TO CONVENTIONAL SWITCHES OF THE SAME GENERAL TYPE.

Jan. 26, 1971 M. J. SAKATOS 3,559,123

' \NONPOLARIZED MAGNETIC REED SWITCH' Filed Dec. 9, 1968 II A v "75" PRIOR ART 4 FIG 1 IO 20 q 26 24 I I '{II '27 25 w I3 I T1 22 INVENTOR MICHAEL J. SAKATOS ATTORNEY United States Patent US. Cl. 335-154 7 Claims ABSTRACT OF THE DISCLOSURE A nonpolarized, single pole, double throw dry reed switch consisting of an elongated envelope which carries three reed members, terminating, respectively, in first, second and third contact elements that are positioned wholly within the envelope. The first contact element is resilient and flexible and projects inwardly from one end of the envelope. The second and third contact elements are essentially rigid, project inwardly from the other end of the envelope and are spaced apart. The free end portion of the first contact element is positioned in the space between the second and third contact elements and normally and yieldingly makes contact with the second contactelement. All reed members, including their contact elements, are homogeneously ferromagnetic. By proper selection of parameters or combinations of parameters, such as the composition and extent of annealing of the reed members and the configuration and arrangement of the contact elements, the present reed switch embodies improved operating characteristics, such as efiective snap action, as compared to conventional switches of the same general type.

' BACKGROUND OF THE INVENTION This invention relates to an improved non-polarized dry reed switch having desirable operating characteristics. The invention pertains, in one of its more specific aspects, to a dry reed switch including three reed members which terminate in corresponding integral contact elements that are positioned within a sealed enevelope, the reed members and contact elements being magnetic.

The switch of this invention is in the general category of dry reed switches which comprise an elongated glass envelope, a first reed member extending through one end of the envelope and spaced second and third reed members extending through the other end of the enevlope. Each reed member terminates in a contact element which is positioned wholly within the envelope. Prior art reed switches of this type include those disclosed in Ellwood Pat. No. 2,264,746 and Burton Pat. No. 2,483,723. At least the contact element of one of the reed members of those switches is non-magnetic.

Since a suitable electrically conductive non-magnetic material, having a coefiicient of expansion which is the same as that of the glass envelope, is not readily and economically obtainable, it has generally been the practice heretofore to make the reed members, except for the non-magnetic contact element of one thereof, of a magnetic material which matches the expansion characteristics of the glass envelope. Such reed switches, while commercially acceptable, are not entirely satisfactory because of several inherent drawbacks and objections.

For one thing, when magentic flux is applied to the switch, the magnetic force of attraction between the mov- ICE able contact element and the normally open contact element must operate against the initial pretension force existing between the movable contact element and the normally closed contact element. As a consequence, the movable contact element tends to hesitate or hang-up between the other contact elements, as the magnetic flux is applied, thereby resulting in undesirable switching characteristics.

Also, since the magnetic contact elements usually employed in known reed switches reach their magnetic saturation level at a relatively low level of magnetic flux density, it has been common practice to minimize the extent of pretension between the movable contact element and the normally closed contact element for the purpose of reducing hang-up. This practice results in insufiicient contact force which creates objectionable electric circuit noise and unreliable contacting between the movable contact element and the normally closed contact element. A low pretension force between the indicated contact elements is additionally objectionable for the further reason that it causes excessive bounce when applied magnetic flux is withdrawn and the contact elements return to their normal relative positions.

The fact that the normally closed contact element is nonmagnetic also contributes to undesirable noise when the applied magnetic flux is withdrawn or substantially reduced. The reason for this is that this contact element is devoid of residual magnetic attraction for absorbing any of the kinetic energy released by the moving contact element in returning to its normal position.

Moreover, if a conventional reed switch is located in or near a field of stray magnetic flux, such as those created by transformers, panels of electric meters, magnets and the like, contact between the movable contact element and the normally closed contact element tends to become and frequently becomes, erratic and unstable.

The reed switch of this invention is intended to and does, in fact, effectively eliminate the drawbacks and objections to conventional switches of the same general type and provides a construction having improved operating characteristics.

SUMMARY OF THE INVENTION The reed switch of this invention comprises an elongated envelope and first, second and third magnetic reeds. The first reed extends through one end of the envelope and is sealed thereto. The second and third reeds extend through the other end of the envelope and are spaced apart and sealed to the envelope. Each reed terminates in a contact element which is positioned in the envelope. The contact elements of the second and third reeds are generally parallel and substantially rigid while the contact element of the first reed is resilient, projects into the space between the second and third contact elements and is normally in contact with the contact element of the second reed. The contact elements are so composed, configured and arranged that, upon application of sufficient magnetic I will be noted from the foregoing that the reeds of the subject invention, including the corresponding contact elements, are magnetic. The term magnetic as used in describing these parts and in the claims includes completely magnetizable materials, such as iron, and any suitable composition comprising a magnetizable material which is clad in a non-magnetizable sheath. Among such compositions that may be advantageously employed in reed switches of this invention is a copper clad iron wire product that is commercially available under the trade name Dumet.

While there are present day reed switches in which all reed parts are magnetic, they are known as magnetically biased switches for the reason that they depend on an external or internal polarizing magnet working in conjunction with an applied magnetic flux field to achieve contact operation. Such reed switches are also referred to as polarized because the direction of armature movement is determined by the polarity of the applied magnetic flux field.

The reed switch of this invention does not require a permanent magnet or other source of subsidiary magnetic flux to react with applied magnetic flux to effect desired movement of the referred-to first contact element. It follows, therefore, that the present switch is not affected by the polarity of the applied magnetic flux and responds identically regardless of flux polarity.

The present reed switch, by virtue of utilizing reed members that are entirely magnetic, is more economical than known related switches. The improved operating characteristics of the switch are attained as the result of one or more novel design features which are capable of causing the net magnetic attraction, during operation, to shift the movable contact element from the normally closed contact element to the normally open contact element. Such design features include one or more of the following:

(1) Varying the magnetic saturation level of the reed contact elements.

(2) The configuration of one or more of the reed contact elements.

(3) Control of the overlap area of the reed contact elements to effect desired shift in operate condition at a predetermined level of magnetic flux.

(4) Controlled flexing of the movable and normally closed contact elements which also results in desirable wipe of contact surfaces.

It is'the primary object of this invention to provide a novel reed switch having improved operating characteristics.

Another object of the invention is the provision of a nonpolarized reed switch in which the several reeds are entirely magnetic.

A further object of the invention is the provision of a switch of the character indicated which is simple and compact in design; which is rugged and durable in construction; which is capable of being manufactured economically in miniature and sub-miniature sizes; and which is adapted to perform its intended switching functions in a dependable and trouble-free manner.

. The enumerated objects and additional objects, as well as the advantages of this invention, will be readily apparent to persons versed in the art from the following detailed description and the accompanying drawing which describe and illustrate a related prior art switch and four embodiments of the inventive switch.

BRIEF DESCRIPTION OF THE DRAWING In the drawing wherein like reference numerals denote corresponding parts in the several views:

FIG. 1 is a magnified view, in central longitudinal cross section, of a typical prior art reed switch;

FIG. 2 is a view corresponding to FIG. 1 of a first rec switch according to this invention and shows a magnetizing coil operatively associated with the switch;.and

FIGS. 3, 4 and 5 are views corresponding to FIG. 1 of 4 second, third and fourth reed switches, respectively, according to this invention.

PRIOR ART REED SWITCH Reference is first had to FIG. 1 which illustrates a typical prior art reed switch that comprises an elongated glass envelope 10 which carries three electrically conductive reed members, namely a first reed member 11 consisting of a first terminal element 12 and a first contact element 13, a second reed member 14 consisting of a second terminal element 15 and a second contact element 16, and a third reed member 17 consisting of a third terminal element 18'and a third contact element 19.

Terminal element 12 of reed member 11 extends through one end of envelope 10 and is sealed thereto. Terminal elements 15 and 18 of respective reed members 14 and 17 are arranged in spaced parallel relationship, extend through the other end of the envelope and are sealed thereto. The several contact elements 13, 16 and 19 are positioned wholly within the envelope, element 13 being resilient and flexible and elements 16 and 19 being essentially rigid. Element 13 normally and yieldingly bears against and forms electrical contact with element 16. Element 13 is adapted, upon energization of a suitable magnetizing coil (not shown), to be flexed upwardly, thereby breaking contact with element 16 and making contact with element 19 in the usual manner.

Reed members 11 and 17 and terminal element 15 of reed member 14 are made of a magnetic material. Contact element 16 of reed member 14, in keeping with prior art teachings as stated earlier herein, is nonmagnetic.

EMBODIMENTS OF THE INVENTION Four recommended embodiments of reed switches constructed in accordance with this invention are illustrated in FIGS. 2 through 5. As will be evident from an examination of the several views, each such embodiment is related to the construction of FIG. 1 in that it comprises a glass envelope 10 and three electrically conductive reed members, corresponding generally to reed members 11, 14 and 17. Certain of the constructions of FIGS. 2 through 5 include reed members which, for purposes of this disclosure and in the interests of simplicity, are the same as earlier described reed members 11 and/ or 17. Each of the illustrated inventive embodiments differs over the prior art (FIG. 1) in at least one important respect, i.e. all reed members, including their contact elements, are magnetic and, consequently, are devoid of any non-magnetic contact elements corresponding to element 16 of FIG. 1.

Referring now to FIG. 2, the reed switch shown therein includes earlier described glass envelope 10 and first reed member 11. The envelope is circumscribed by a conventional magnetizing coil 20. The switch is also provided with a second reed member 21 consistingof a second terminal element 22 and a second contact element 23 which is the same as contact element 16, except that it is magnetic, and a third reed member 24, corresponding to earlier described reed member 17. Reed member 24 consists of a third terminal element 25 and a third contact element 26 which terminates in an end part 27 that projects downwardly toward first contact element 13.

The configuration of end part 27 is not due to the contact surface material, which is normally less than millionths in thickness, but is the contact part of reed member 24. Its purpose is to concentrate the available magnetic flux to attract contact element 13. It is well known in the art that reducing the surface area of magnetic pole faces concentrates flux, thereby achieving higher mechanical tractive force. This is a common practice in the electromechanical relay industry.

Turning next to FIG. 3, the construction shown therein is the same as that of FIG. 1 except that it utilizesa differently configured wholly magnetic second reed member 28 in place of partly magnetic reed member 14."Reed member 28 consists of a second terminal element 29 and a second contact element 30 having an upwardly and forwardly projecting free end part 31 that is normally in contact with movable contact element 13, as shown.

The embodiment shown in FIG; 4 differs over the construction of FIG. 1 primarily as regards the composition of second reed member 32 'which, here again, is wholly.

magnetic. Reed member 32 consists of a second terminal element 33 and a secondcontact'element 34. It will be observed that the overlap between contact elements 34 and 13 is greater than that between contact elements 16 and 13 (FIG. 1).

In the prior art, as represented by FIG. 1, the second contact element 16 is non-magnetic in nonpolarized magnetic reed switches. In my FIG. 4, reed member 32 is composed of magnetizable material identical with or similar to the other two reed members contained in the switch capsule, which is a major departure from prior art. A further deviation is the amount of overlapping surface area in parallel contact between contact element 13 and reed member 32. Reed member 32 has a relatively long overlap with reed member 13, resulting in a large pole surface area. It is well known that a large pole surface area tends to spread the available-flux, making the magnetic force of attraction less efiicient. This is the very feature desired for the normally closed contacts, reed members 32 and 13, so that a minimum amount of resistance will be offered to the attraction of contact element 13 to contact element 19, which exhibits a smaller, and therefore more concentrated, flux area.

' Referring now to FIG. 5, the switch construction illustrated therein differs over that of FIG. 4- as regards its first reed member 35 which correspondsto reed member 11. Reed member 35 consists of a first terminal element 36 and a first contact element 37 having an ofifset free end part 38.

Again having reference to the embodiment of the invention of FIG. 3, the moment arm of the portion of the contact element 13 to the part thereof immediately above element 31 is smaller than the moment arm of the complete contact element 13. In addition, the contact area with the surface of 31 becomes saturated with flux passing through the portion of 13 at its-interface with 31 and through reed member 28, leaving the portion of element 13 from above 31 and below 19 literally without flux except for the amount passing through reed 17 at contact element 19. Flux in the gap below contact element 19 will continue to build up to a point at which sufficient tractive force .is developed to pull reed 13 to make closure with 19. At this instant as reed'13 begins to move upwardly, the reluctance of the air gap at interface 19 decreases while that at interface 31 increases, and contact element 13 moves into contact with contact element 19 by snap action. A similar arrangement and condition occur in the embodiments shown in FIGS. 4 and 5.

Based on the foregoing, it is believed that the construction, operation, objects and advantages of this present invention will be readily comprehended by persons skilled in the art, without further description. It is to be clearly understood, however, that various changes in the constructions described above and illustrated in the drawing may be made without departing from the scope of the invention, it being intended that all matter contained in the description or shown in the drawing shall be interpreted as illustrative only and not in a limiting sense.

I claim:

1. In a nonpolarized electrical reed switch:

(a) an elongated envelope; and

(b) a plurality of entirely magnetic reed members extending through and sealed to selected ends of the envelope and comprising:

(1) a first reed member extending through one end of the envelope and terminating in a first contact element within the envelope, and

(2) spaced second and third reed member extending through the other end of the envelope and terminating in respective second and third contact elements within the envelope;

the first contact element projecting into the space between the second and third contact elements and normally and yieldingly making contact with the second contact element; said second contact element having a lower saturation level than said third contact element, said contact elements being so composed, configured and arranged that, upon application of sufficient magnetic flux thereto whereby the magnetic attraction between the first and third contact elements is greater than that between the first andsecond contact elements, the first contact element moves to break contact with the second contact element and make contact with the third contact element.

2. The reed switch of claim 1 wherein each reed member is composed of a homogeneous ferromagnetic material. 3. Thereed switch of claim 1 wherein the first contact element moves, upon application of magnetic flux, as stated therein, by snap action.

4. The reed switch of claim 1 wherein the second contact element includes a free end part which projects toward the first contact element and normally contacts a portion of the first contact element which is spaced from its free end.

5. The reed switch of claim 1 wherein the contact elements are substantially rectilinear and parallel and wherein the contact area between the first and second contact elements is substantially greater than the contact area between the first and third contact elements when the switch is energized.

6. Ina nonpolarized electrical reed switch:

(a) an elongated envelope; and

(b) a plurality of magnetic reed members extending through and sealed to selected ends of the envelope and comprising:

(1) a first reed member terminating in a first contactelement within the envelope; and (2) spaced second and third reed members terminating in respective second and third contact elements within the envelope; the first contact element projecting into the space between the second and third contact elements and normally and yieldingly making contact with the second contact element, the third contact element including a free end part which projects toward the second contact element, said contact elements being so composed, configured and arranged that, upon application of sufficient magnetic flux thereto whereby the magnetic attraction between the first and third contact elements is greater than that between the first and second contact elements, the first contact element moves to break contact with the second contact element and make contact with the third contact element.

7. In a non-polarized electrical reed switch:

(a) an elongated envelope; and

(b) a plurality of magnetic reed members extending through and sealed to selected ends of the envelope and comprising:

*( 1) a first reed member terminating in ,a first contact element within the envelope; and

(2) spaced second and third reed members terminating in respective second and third contact elements within the envelope;

the first contact element projecting into the space between the second and third contact elements and normally and yieldingly making contact with the second contact element; the first contact element including a free end part which is offset from the remainder thereof, which is at all times out of contact with the second contact element and which is adapted to make contact with the third contact element upon energization of the switch; said contact elements being so composed, configured and arranged that, upon application of sufficient magnetic flux thereto whereby the magnetic attraction between the first and third conmentvandmake contact with the third contact element. 7

2 References Cited STATES PATENTS I UNITED 8/1964 Ohki et a1. 33s 1s4X 1/1966 Sakatos 335-154 3/1967 Ellwood et a1 335-151LX 6/1968 Insley 335--151X FOREIGN PATENTS 3/1960 Germany 335-154 BERNARD GILHEANY, Primary Examiner R. N. ENVALL, JR., Assistant Examiner 

